raindancewx

Cold ENSO with low sea ice since 2007...v. Cold ENSO with (relatively) high sea ice since 2007. Really curious to see if this works in 2020. I don't really look at 2007, 2012, and 2016 as similar...they are very different ENSO events. But they all have the low-sea ice and cold West. I put 2011 in both because it was cold in NM/TX at the border of the two cold areas, and the 4.3m square km also seems to be the borderline threshold for this. The ACE index is higher on the left image, so maybe this is just all an Atlantic thing, since both sea ice and ACE are tied broadly to the AMO.

This is the Euro plume from October 1 for the La Nina. I've drawn in my expectations - I think this event could peak pretty strong. But I also think the Euro is right about a pretty quick turnaround/warm up after January.

I mean...I've seen 90 point dew point depressions here. You all are just spoiled up there. The -PDO can really dry things out in the West if it lasts long enough, and Nino 4 finally getting knocked below average helps too. The dew points here tend to run in the 30s/low 40s into October in a good monsoon year most days. When the monsoon fails it seems like dew points run from 10-30 most of the time in Fall. That's one reason I don't think it's a super hot winter though. It's going to be pretty dry, but with semi-regular cold fronts I think. So cold air moving in when dew points are -10, 0, 10, 20, etc. is a recipe for some pretty cold nights. I've been looking at precipitation patterns by hurricane season activity here. December has a near 0 chance of topping average precipitation in a very active hurricane season (>160 ACE) in a La Nina. But it has a 50% chance in the other La Ninas, going back to the 1930s. The difference is statistically significant (p is 0.037 or so), and none of the other cold months are even close to that. ACE is still only at 111 despite 25 named systems. So December has a decent shot at being a good month. Not really optimistic about November even though I kind of expect a big cold dump in late October, probably the week before Halloween. I kind of get the impression there will be a good storm or storms by the end of October for much of NM, CO, WY.

ACE on the CSU site has updated at least twice today and is currently 111.4 as of late Tuesday. It seems generally you add 1 point for a weak tropical storm that lasts all day, 2 for a weak hurricane that lasts all day, 3 for a major hurricane, and 4 for a category 5. This system has four days left until it dies, so the ACE should get into the low 120s, which is still the mid point of the 80-160 La Nina composite favoring a cold NW. By 10/10, the season is typically 85% or more over, but it can be less, and it can be more. I lean toward a couple more tropical storms after Delta, but this is probably the last big system this year. You'll probably see some big weakening if Delta hit Mexico, and then a larger, weaker hurricane after. The Gulf of Mexico is pretty spent at the moment, so it is fairly cold. So I lean toward 2.5 points a day for the next four days from Delta. We'll see how close 10/10, at 5 pm MST is to 121 ACE. I'm planning to release my outlook 10/10. I've got 50+ slides this year, but most of it is pictures. I've got a pretty hot winter in some parts of the South - mostly the coastal SE and especially Texas. I have the interior West cold, but not that cold. I have most of the East warm, but still much colder than last year. Statistically, the odds of a wet December here are near 0% if the ACE is above 160, and near 50% if the ACE is under 160 in La Ninas over the past 90 years. So do want to see how high the ACE gets. Since mid-September my outlook has assumed years with 95-175 Atlantic ACE would be similar, given about 135 ACE this year.

As best I can tell, there are only 17 hurricanes to hit the US Gulf Coast in October since 1931. It's interesting to see 1964 show up as one of the years (Hilda), with one of the once a decade non-Florida hurricane landfalls on the Gulf in October. Have to see if Delta actually follows the current projected track. The closest tracks since 1931 in October to Delta are probably Nate (2017), Hilda (1964), Opal (1995), Lili (2002), and Jerry (1989). Of those years, 1964 is the only one with a warm NW October though (currently 5-10 above normal in some places in Oregon).

This is going to be a really weird winter for our region. Pretty sure of that. The storms are finally starting to show up in the long-range for the Northwest, which is good, that was what I expected. My best guess is the NAO will go negative, either substantially but only for a small time, or only a bit, but for an extended period, in December. I've had some good success using this method in prior years. March would likely be pretty negative too. My sense is the intense heat of Summer will show at times in winter, but you'll also see very intense waves of cold show. The worst case scenario for us would be that my reliance on ENSO order is irrelevant, and years like 2008, 1999, 1975, 2017 end up taking over somehow, instead of the La Ninas that follow El Ninos like 2016, 2010, and 2007 - relatively wet years generally.

General warming again in Nino 1.2 Way ahead of 2016 and 2017, 2008 at this point. Somewhat colder than 2011 too most spots. Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 02SEP2020 18.9-1.6 23.6-1.3 25.8-0.9 28.4-0.3 09SEP2020 19.5-1.0 23.4-1.4 25.7-1.0 28.5-0.2 16SEP2020 20.0-0.4 23.6-1.3 25.9-0.8 28.2-0.4 23SEP2020 19.6-0.8 23.6-1.2 25.7-1.0 28.1-0.5 30SEP2020 20.1-0.5 23.8-1.1 25.6-1.1 27.9-0.7 30AUG2017 20.3-0.2 24.5-0.4 26.5-0.2 28.8 0.2 06SEP2017 20.4-0.1 24.3-0.6 26.2-0.6 28.7 0.1 13SEP2017 19.7-0.7 24.0-0.9 26.1-0.6 28.7 0.0 20SEP2017 19.3-1.1 23.9-1.0 26.3-0.4 28.7 0.0 27SEP2017 19.5-1.0 24.4-0.5 26.5-0.2 28.4-0.2 31AUG2016 20.9 0.3 24.6-0.3 26.0-0.7 28.5-0.1 07SEP2016 20.8 0.3 24.6-0.3 26.1-0.7 28.6-0.1 14SEP2016 20.6 0.2 24.7-0.2 26.1-0.6 28.5-0.2 21SEP2016 21.2 0.8 24.8-0.1 26.3-0.4 28.5-0.2 28SEP2016 21.2 0.6 24.7-0.2 25.9-0.8 28.1-0.5 31AUG2011 20.0-0.5 24.4-0.5 26.1-0.7 28.3-0.4 07SEP2011 19.7-0.7 24.2-0.7 26.1-0.7 28.2-0.5 14SEP2011 19.6-0.8 24.1-0.7 26.0-0.8 28.0-0.7 21SEP2011 19.8-0.6 24.3-0.6 25.9-0.9 27.8-0.9 28SEP2011 19.9-0.6 24.1-0.7 26.0-0.7 28.0-0.7 03SEP2008 21.3 0.8 25.3 0.4 26.6-0.2 28.1-0.6 10SEP2008 21.0 0.6 25.2 0.3 26.6-0.2 28.1-0.6 17SEP2008 21.1 0.8 24.9 0.1 26.4-0.4 28.1-0.6 24SEP2008 21.3 0.8 25.1 0.2 26.4-0.4 28.1-0.6 01OCT2008 21.0 0.4 24.7-0.2 26.2-0.5 28.3-0.4 Still way warmer than 2010 though in all zones. 01SEP2010 18.8-1.7 23.4-1.5 25.1-1.7 27.2-1.5 08SEP2010 19.1-1.3 23.5-1.4 25.2-1.6 27.1-1.6 15SEP2010 18.6-1.8 23.4-1.5 25.1-1.6 27.1-1.6 22SEP2010 19.3-1.2 24.0-0.8 25.1-1.6 27.1-1.6 29SEP2010 19.2-1.4 23.5-1.3 24.8-1.9 27.1-1.6 06OCT2010 18.7-1.9 23.2-1.7 24.8-1.9 27.1-1.6 Very close to 2007 in Nino 3.4 and identical in 4. Pretty different in Nino 1.2 - but 2007 warmed up a lot there in December, so might snap back toward 2007 then. 1995 is close too. 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 12SEP2007 18.6-1.8 23.6-1.3 25.8-1.0 28.0-0.6 19SEP2007 18.5-2.0 23.6-1.2 25.8-0.9 28.0-0.7 26SEP2007 18.4-2.1 23.2-1.7 25.6-1.1 28.0-0.7 03OCT2007 18.3-2.3 23.2-1.7 25.4-1.3 27.9-0.7 06SEP1995 20.4 0.0 24.1-0.8 26.0-0.8 28.2-0.5 13SEP1995 19.9-0.5 24.1-0.8 26.0-0.7 28.0-0.6 20SEP1995 20.2-0.2 24.0-0.9 26.1-0.7 28.4-0.3 27SEP1995 20.2-0.3 23.9-1.0 25.9-0.8 28.4-0.3 30SEP2020 20.1-0.5 23.8-1.1 25.6-1.1 27.9-0.7 The September NAO was more positive than I expected. When I run my NAO script, it suggested several possible blends, but I think this one is probably the best for what it will do: 2020: 1961, 2003, 2007. March would also be somewhat negative in this scenario. In prior years, 1993, 2017, 2017 was a good blend for 2019. Generally, you look for the best match that has similar ENSO tendencies for May-Apr and Sept-Mar for the NAO state. If you don't have a good ENSO match available because of some unusual combination of NAO changes, the best blend overall will typically work, based on testing from 1995-2019. 1975 is a good match to 2018 1990, 1990, 1994 was a good match for 2017 2004, 2010, 2011 was a good match for 2016 1992, 1994 was a good match for 2015.

All of the Nino zones came in below the 1951-2010 historical averages in September. Compared to September 2007, the current La Nina is consistently 0.2-0.4C warmer in all zones Nino 4 Nino 3.4 Nino 3 Nino 1.2 2007 28.11 25.61 23.63 19.75 2020 28.28 25.96 23.93 19.54 In the 1950-2019 data, you don't have any years where Nino 3.4 dropped off by more than ~1.0C from September to Dec-Feb. So it's pretty likely this event will come in 25.0C or warmer, as the subsurface data had previously implied. I think a couple months could come in around 25.5C - but we'll have to see.

There seem to be two areas impacted by the QBO in the US from what I can see. For whatever reason, there is a pretty big difference in the South Central US between La Ninas with a QBO -2 or lower and La Ninas with a QBO +2 or higher. The same NW areas are still cold though. The years with a drop off in QBO values in Summer (JJA) to Winter (DJF) seem to feature at least some cold dumps into the central US more reliably. So that's the coldest La Nina/QBO composite I could find. The rising QBO years are more amplified, with broader warmth and cold in the NW. We aren't in the first situation. The QBO was about 0 in JJA and rising. That map (rising) as a composite gives the same features as winters with a QBO >2. So unless you live in Kansas, most areas are pretty similar regardless of what you do with the QBO. These composites are so small and erratic, that I'd say they mean almost nothing in aggregate. I did draw in some dummy high/low positions without checking the maps as a guess for how the composites might be varying. I'm personally much more interested in the ACE value for the Atlantic at this point. The long-term average is about 105.6 so we're still technically below an average season (1981-2010), and La Ninas average 128 ACE from 1930-2019. October averages about 15 ACE, and I doubt there has ever been an October ACE over 50. Locally, there is a very strong correlation in La Nina years to how cold we get at the coldest time of the year here - Dec 16-Jan 15, when the average high is 46 and the average low is 24. So quite curious to see how high the ACE gets. The projected mid-Dec to mid-Jan value high on the image below is reliably (~5/6) within 3.3 degrees of observations, and actually tends to be a lot closer than that if ACE isn't under 65 or so where most of the outliers are. I've looked at Neutral and El Nino years here, and you don't have a relationship like this in any month from October-May. The relationship holds well over time too - 1933 is the dot furthest to the right with the highest ACE. My sense is a low ACE La Nina went into phases 4-5-6 fairly often during the heat of the hurricane season. Five, or the "five look" with a warm Nino 4 can be very cold here if it shows up again in late December like in 2007. Below the surface, 100-180W looks a lot like a combination of 2003, 2007, 2010, 2017 for July-September, and the match is fairly close to what the models show for October and how September ended up. I'm not a fan of 2010 and 2017, they both have timing and severity issues. There are non-ENSO things I like about 2003, but can go more into that when I put my outlook up in a week or two. https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ocean/index/heat_content_index.txt

Canadian has a long lasting La Nina that gradually becomes centered pretty far West. It trended stronger than before. Nino 4 would stay cold for a long time in this depiction - that hasn't happened in close to a decade. The monthly sea surface temperature readings for the September monthlies should look a lot like 2007. On the Canadian, the cold ring by NW North America tries to develop around the warm tongue east of Japan. That'd be a pretty healthy and canonical -PDO, which is a pretty warm signal for the SE. Good for the NW to be cold. Pretty strong dry signal in the SW, especially Fall and Spring, locally it peaks as an indicator in November and May.

Still looks a lot like 2007, especially in Nino 3.4 and 4. Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 12SEP2007 18.6-1.8 23.6-1.3 25.8-1.0 28.0-0.6 19SEP2007 18.5-2.0 23.6-1.2 25.8-0.9 28.0-0.7 26SEP2007 18.4-2.1 23.2-1.7 25.6-1.1 28.0-0.7 02SEP2020 18.9-1.6 23.6-1.3 25.8-0.9 28.4-0.3 09SEP2020 19.5-1.0 23.4-1.4 25.7-1.0 28.5-0.2 16SEP2020 20.0-0.4 23.6-1.3 25.9-0.8 28.2-0.4 23SEP2020 19.6-0.8 23.6-1.2 25.7-1.0 28.1-0.5 October is depicted like a relatively canonical MJO phase five October, and an almost identical match to 1964 on the CFS

September looks like it will finish near average for temperatures here. One of the driest monsoons since 1931 for Albuquerque. The current October forecast on the CFS is very similar to 1964. Relatively canonical MJO phase five look for October, which makes sense as October is expected to be in phase five initially.

Nino 4 looks like it is cooling at the surface, but still pretty warm below. It does look like the cold is bleeding West, which is what the models show, and what happened in years like 2007.

I don't do Fall outlooks, but if I had done a Fall outlook, you really can't find a better match long-term than 1995 for the Nino zones. But I do expect 2007 to take over later in the fall. This is Nino 3.4 1995 27.57 27.49 27.75 28.10 27.82 27.59 27.08 26.23 2007 27.24 26.88 27.10 27.50 27.46 27.37 26.71 26.14 2020 27.14 27.11 27.76 28.17 27.65 27.38 26.99 26.30 Nino 4 - 1995 29.04 28.91 29.03 29.14 29.31 29.18 28.93 28.65 2007 28.97 28.66 28.66 28.73 28.84 28.90 28.68 28.48 2020 29.16 28.97 29.07 29.15 29.00 29.09 28.89 28.50 The biggest problem with 1995 is the PDO I think - 2020-03-01T00:00:00Z -0.82 2020-04-01T00:00:00Z -0.57 2020-05-01T00:00:00Z 0.09 2020-06-01T00:00:00Z -0.08 2020-07-01T00:00:00Z -0.38 2020-08-01T00:00:00Z -0.28 https://oceanview.pfeg.noaa.gov/erddap/tabledap/cciea_OC_PDO.htmlTable?time,PDO 1995-03-01T00:00:00Z 0.75 1995-04-01T00:00:00Z 0.83 1995-05-01T00:00:00Z 1.46 1995-06-01T00:00:00Z 1.27 1995-07-01T00:00:00Z 1.71 1995-08-01T00:00:00Z 0.21 90% of the time, maybe more, the PDO values are -2 to +2. So +1.7 in July 1995 and -0.4 in July 2020 is a massive difference. Even the August difference is still pretty substantial. It popped back up too - to +1.2 in September, and on/off again was pretty positive through Spring. Nino 1.2 has been warming. If that continues into October, then the PDO won't go as negative as it looked a few weeks ago. If it really warmed up a lot, it might even go positive, but I don't expect that. You can see cooling lately in some of the areas you'd want for a -PDO on Tropical Tidbits (by the coast of Western Canada), but also hints of cooling east of Japan where you'd want cooling for the +PDO. This is what I have tentatively for winter, with the analogs removed, since people need to come up with their own ideas - Here is how the analog package looks compared to September. It is also similar on solar, ENSO trends, and actual US temperatures for July-September (assuming the forecast NE/Western heat continues to burn off cold in those areas). You can see that the transition in the La Nina is the same in my analogs as on the CFS. I was a bit surprised to see the cold eastern Atlantic show up in September in both 2020 and the analogs, because it definitely warms up by winter.

The analogs I have look like the -QBO years because 2007 is the analog I trust most, even though it is still flawed. However, late winter and spring do look like the +QBO years on my blend for the winter. 2007-08 had a -QBO but it was rising, like this year. I find that the trend is about as reliable as the actual QBO anomaly for large areas of the country. I'm skeptical to bet the farm on only ENSO/QBO DJF seasonal averages. To me 2010-11, 1995-96, 1988-89, 1973-74, 1964-65 are also very different winters. I actually don't consider 1995 a bad analog, but it's mostly for how similar the ENSO has been all year, not the surrounding stuff like the PDO or AMO. It's not going to be similar on hurricane activity either, we're at less than half the 1995 total ACE in the Atlantic to date even with 23 named systems. Here is how these years looked for the QBO v. 2020, to me, they look very different with unusual tendencies in 2020 that would suggest erratic QBO behavior later on. I don't have QBO data at 45mb, but this is 30mb. 1964 3.94 5.26 5.46 5.94 6.32 2.23 -0.56 -0.57 -0.67 0.42 0.71 0.04 1973 -4.40 0.08 3.40 6.28 8.12 8.63 6.94 5.86 5.51 5.20 4.92 2.31 1988 7.81 6.17 5.86 6.59 5.46 0.42 -3.96 -2.58 -2.29 -1.53 -0.84 -2.42 1995 8.38 8.01 8.79 11.79 14.92 15.62 11.74 9.53 6.98 3.43 -0.77 -4.57 2010 -16.02 -16.98 -19.68 -23.57 -26.28 -25.05 -9.84 1.45 6.58 10.83 12.16 10.97 2020 -2.51 -3.20 -4.36 -5.03 -4.86 -2.78 0.34 4.78 -999.00 -999.00 -999.00 -999.00 64 up up up up down down down down 73 up up up up up down down down 88 down down up down down down up up 95 down up up up up down down down 10 down down down down up up up up 2010 down down down up up up up up You can see trend wise, 1964 is backwards (opposite) as is 1973. 1995 trended down mid-year, while we are trending up. You do have the right idea for Jan-Aug in 2010, but the QBO looks to me like it will keep going up the rest of the year. It didn't in 2010. Does that matter? Maybe? The magnitudes seem like they could be pretty close in 2010 through Fall and then be very different in winter. If you care about the trend I think 2016 is probably better than 2010 as a match. At a high level, I know 2010 and 1988 were both active monsoon years, without record setting heat in the West in the Summer. 1995 is closer in that regard too. To me, if the QBO was meaningfully similar through August, you wouldn't see something like a near all-time strong Western Monsoon in 1988 and a near all-time weak Western Monsoon in 2020. Some of that is solar driven, but the QBO is supposed to impact tropical weather and by extension subtropical weather like the monsoon. I think part of it is Nino 4 dropped much faster in 2010 and 1988 than this year. It had dropped like from 29.5 to 27.5 or something in 2010 January to August. It's only fallen 0.6 or so this year. My real issue with 2010 is you're talking about a ~3C year/year drop in Nino 3.4 We're not getting that this year, this isn't the La Nina version of 2015-16. Even 1988 had like a 2.5C drop. I'm looking for like a 1.6C drop y/y (27.1C to 25.5C).If you pulled up August 1964, it was super cold in the entire West - complete opposite this year. 1973 is warmer, but still nothing like this year. In 1995, you have a similar looking August and September nationally, with the slower decay of Nino 4 like in 2007 and this year.

This is the updated subsurface comparison to 2007. To me it kind of looks like 2007 but everything happens 4-8 weeks later. So maybe the September flat-line in 2020 is the 2007 flat-line in August, and then the La Nina peaks in October? I guess we'll see. It's possible though that we really won't see much change in the subsurface for a while.

Mathematically, I'd say for relevance, if you scored the 11 La Ninas for similarity to this year in the third weekly reading for September, you'd rank it like this, with Nino 1.2 difference multiplied by one, Nino 3 and 4 multiplied by two, and Nino 3.4 multiplied by three. 2005, 2010, 2016 are the worst matches, with 1995, 1999, 2000, 2007, 2011 the top matches. September does look a lot like 1999 at the moment. The models favor the La Nina becoming centered west of where it is now, which is consistent with current observations and how 2007 developed. My analogs look a lot like July, August and September nationally with the same kind of East core Fall to Central core Winter look the Jamstec/CFS show for the La Nina, so that's why I'll be riding 2007 fairly hard, even though it should be a weaker La Nina overall. Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 20SEP1995 20.2-0.2 24.0-0.9 26.1-0.7 28.4-0.3 (0.2) + (0.4 x 2) + (0.2 x 3) + (0.2 x 2) = 2.0 23SEP1998 20.5 0.1 24.1-0.7 25.5-1.2 27.6-1.1 (0.5) + (0.5 x 2) + (0.7 x 3) + (0.6 x 2) = 4.8 22SEP1999 19.3-1.2 23.8-1.1 25.8-0.9 27.9-0.7 (0.7) + (0.2 x 2) + (0.1 x 3) + (0.3 x 2) = 2.0 20SEP2000 20.1-0.3 24.2-0.6 26.1-0.6 28.5-0.2 (0.1) + (0.6 x 2) + (0.2 x 3) + (0.3 x 2) = 2.5 21SEP2005 19.6-0.9 24.7-0.2 26.8 0.1 28.9 0.3 (0.4) + (1.1 x 2) + (0.9 x 3) + (0.7 x 2) = 6.7 19SEP2007 18.5-2.0 23.6-1.2 25.8-0.9 28.0-0.7 (1.5) + (0.0 x 2) + (0.1 x 3) + (0.2 x 2) = 2.2 24SEP2008 21.3 0.8 25.1 0.2 26.4-0.4 28.1-0.6 (1.3) + (0.4 x 2) + (0.8 x 3) + (0.1 x 2) = 4.7 22SEP2010 19.3-1.2 24.0-0.8 25.1-1.6 27.1-1.6 (0.7) + (0.4 x 2) + (0.8 x 3) + (1.1 x 2) = 6.1 21SEP2011 19.8-0.6 24.3-0.6 25.9-0.9 27.8-0.9 (0.2) + (0.7 x 2) + (0.0 x 3) + (0.4 x 2) = 2.4 21SEP2016 21.2 0.8 24.8-0.1 26.3-0.4 28.5-0.2 (1.2) + (1.2 x 2) + (0.4 x 3) + (0.3 x 2) = 5.4 20SEP2017 19.3-1.1 23.9-1.0 26.3-0.4 28.7 0.0 (0.7) + (0.3 x 2) + (0.4 x 3) + (0.5 x 2) = 3.5 16SEP2020 20.0-0.4 23.6-1.3 25.9-0.8 28.2-0.4

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 05AUG2020 19.8-1.2 24.6-0.6 26.3-0.6 28.4-0.3 12AUG2020 19.9-0.9 24.8-0.3 26.4-0.5 28.3-0.4 19AUG2020 19.5-1.1 24.3-0.7 26.0-0.8 28.4-0.2 26AUG2020 20.0-0.6 24.2-0.7 26.1-0.7 28.6-0.1 02SEP2020 18.9-1.6 23.6-1.3 25.8-0.9 28.4-0.3 09SEP2020 19.5-1.0 23.4-1.4 25.7-1.0 28.5-0.2 16SEP2020 20.0-0.4 23.6-1.3 25.9-0.8 28.2-0.4 01AUG2007 19.6-1.5 24.1-1.2 26.4-0.6 28.7 0.0 08AUG2007 19.3-1.6 23.8-1.3 26.2-0.7 28.6-0.1 15AUG2007 19.7-1.0 24.0-1.0 26.3-0.6 28.6-0.1 22AUG2007 19.2-1.4 23.8-1.2 26.1-0.7 28.5-0.1 29AUG2007 18.4-2.1 23.7-1.3 26.1-0.7 28.4-0.2 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 12SEP2007 18.6-1.8 23.6-1.3 25.8-1.0 28.0-0.6 19SEP2007 18.5-2.0 23.6-1.2 25.8-0.9 28.0-0.7 Still pretty similar to 2007. Although Nino 1.2 is warming it looks like. Also, the Nino 4 readings are warmer than 2007. Way colder than 2017, 2016 at this point. Nino 3 is also a lot colder than 2011. All that said, still well behind how cold Nino 3.4 and 4 were in 2010 by this time. Looks substantially colder in some zones than 2000, 2005, 2008 too.

It's been interesting trying to find a good match to the September 2020 US temperature pattern. It's pretty unusual to get a core of heat in the NW with a cold Central US look in September in a La Nina. Some El Nino years are actually similar: 1953, 1957. 1987, 1991 aren't terrible either. Neutral years 1966 and 1967 are both very hot in the NW, but very cold - way too cold - in the Southeast in September. 1974 also fits this description (probably near record heat NW but also record cold TX). 1975 too. 1993 is kind of the right idea, cold middle, warm east/west, but the cold is too far east. Same in El Ninos 2006, 2009. La Nina years like 1933 and 2017 are actually near opposite - which I find encouraging as they are terrible Western winters - top five for heat and dryness in most places. The closest La Nina September is probably 1999. September 2008 is kind of the right idea, but not as extreme as this year. 2011 is like 1993, too far east. A lot of the cold anomalies will burn off in the Rockies by the end of the month - so this may end up pretty close, especially if the South cools a bit with the wetness in the 6-10 day outlooks. You can see a lot of the same weird features - heat core in Oregon, SD/Kansas colder than Nebraska relatively. Summer 1999 was extremely cold in the Southwest, so I don't really think it's a good analog for winter, which gets at how strange this month is. Outside the Northeast, 1999 is almost opposite to 2020 for Summer, but similar in September. We're definitely very different from 1933 & 2017 - cold core Oregon warm core Minnesota - exact opposite of this year for the western 2/3 of the US. Anti 1933/2017 is fairly close (but too cold) to my winter idea at this point.

Nino1+2 Nino3 Nino34 Nino4 Week SST SSTA SST SSTA SST SSTA SST SSTA 05AUG2020 19.8-1.2 24.6-0.6 26.3-0.6 28.4-0.3 12AUG2020 19.9-0.9 24.8-0.3 26.4-0.5 28.3-0.4 19AUG2020 19.5-1.1 24.3-0.7 26.0-0.8 28.4-0.2 26AUG2020 20.0-0.6 24.2-0.7 26.1-0.7 28.6-0.1 02SEP2020 18.9-1.6 23.6-1.3 25.8-0.9 28.4-0.3 09SEP2020 19.5-1.0 23.4-1.4 25.7-1.0 28.5-0.2 08AUG2007 19.3-1.6 23.8-1.3 26.2-0.7 28.6-0.1 15AUG2007 19.7-1.0 24.0-1.0 26.3-0.6 28.6-0.1 22AUG2007 19.2-1.4 23.8-1.2 26.1-0.7 28.5-0.1 29AUG2007 18.4-2.1 23.7-1.3 26.1-0.7 28.4-0.2 05SEP2007 19.4-1.1 23.7-1.2 26.0-0.8 28.3-0.4 12SEP2007 18.6-1.8 23.6-1.3 25.8-1.0 28.0-0.6 Still almost identical in Nino 3 and Nino 3.4 to 2007. But Nino 4 has fallen behind. There was actually pretty substantial warming in Nino 1.2 too. Nino 3.4 has also fallen a tiny bit relative to 2007 now too.

This is a top five cold start to September here since 1931, through 9/13 (~43% of the month). Will be very curious to see if we can finish with a cold September. It does look warmer for the next week, but no 90s in the forecast. Any incoming smoke from the West Coast fires could also hold down temperatures during the day if it makes it out here in a thick plume.

My take is a weaker version of 2007 is the right idea. But I'm open to a stronger La Nina if the event can keep pace this month with 2007 in September. The bottom really fell out in 2007 in the Fall. That's the real test. The warm western Nino 4 subsurface was still there in 2007, even well into September - The models missed how strong it got: -1.5C ONI (forecasts were generally -0.5 to -1.0) I mentioned earlier, if you plot August subsurface against Dec-Feb SSTs in Nino 3.4, you get 25.75C as the estimated strength of the La Nina, give or take 0.75C, at about 80% certainty. So below 2007-08 (25.0C in winter in Nino 3.4) is pretty unlikely. But it wouldn't really be too shocking if it got close to that strong. My instinct is this event will be strongest in Fall, maybe as low as 25.5C or something in September, October or November given that week one of September was 25.8C on the weeklies. Nino 4 and the PDO are both the coldest they've been in a while, which is almost like an indication that the system is less resistant to a stronger La Nina than it has been in a while.

I had kind of forgotten about this since it didn't apply last year, but La Nina after El Nino is a pretty consistent and reliable cold signal for the interior Northwest. In the last 10 cases, an area by Idaho, Wyoming, and Oregon is always either cold, or near average, even in cases when the US is mostly torching. If you look at the areas north of the San Francisco to SD-NE line, that zone is never completely warm in any of the ten most recent La Nina after El Nino winters. There is also a pretty strong warm signal for Texas - 7/10 years feature +3 or hotter winters somewhere in Texas. Even Florida and the Southwest don't have that. The three composite looks that show up by month - cold interior West, cold Northwest, cold NW to Midwest - I actually have analogs that support all three to some extent. So it looks pretty reasonable to me. I think the January look is the closest to what will happen of the three months, but still want to see how the observations in September in the tropics pan out.

Using the 1951-2010 averages, Nino 4 has only been cooler than average for four months since mid-2012. It has been tracking similarly to 2007 this year. Will be interesting to see if that can continue for a while. A much cooler Nino 4 in September means the US should be a lot warmer than last October in most places too. 2007 28.97 28.66 28.66 28.73 28.84 28.90 28.68 28.48 28.11 27.91 27.61 27.42 2020 29.16 28.97 29.07 29.15 29.00 29.09 28.89 28.50 average 28.08 27.97 28.07 28.33 28.63 28.65 28.55 28.41 28.40 28.42 28.39 28.27 My sense is Nino 4 will have trouble falling below 28.0C this Fall-Spring. But we'll see. Still warm below Nino 4 after all.

High was only 55 today once again. So around ~30 degrees below average for the high. This is one of the coldest starts to September here on record, at least for highs. I think it's 6th place - 81.5F (down from 89.1F as recently as 9/8). Based on the historical 9/11-9/30 data for 1931-2019, roughly ~40% chance of a cold month (2F below average high or colder), less than 5% chance of a hot month (2F above average high or hotter), but still most favored for +/-2F compared to average. The high tomorrow is supposed to be in the 70s, so should drag the monthly average down some more.